Slurry additive for ablative water fire extinguishing systems

ABSTRACT

A shelf stable slurry for injection into ablative water fire extinguishing systems comprises a uniform suspension of polyacrylamide polymer gelling agent in a polyoxyalkylene vehicle containing a stabilizing amount of silica suspending agent.

I United States Patent 1151 3,666,707 Livingston 1 May 30, 1972 [54]SLURRY ADDITIVE FOR ABLATIVE 3,354,084 11/1967 Katzer 252/2 WATER FIREEXTINGUISHING 2,892,730 6/1959 Kloepfer. 106/ 193 SYSTEMS 2,760,9418/1956 Iler ..260/2.5

3,210,273 10/1965 Taulli ..252/28 [72] Inventor: William L. Livingston,Sharon, Mass. 3,474,061 10/1969 Benin at "260/29 6 73 Assigneez FactoryMutual Research Corporation, 3,514,500 3/1970 Osmond ..260/8 74Turnpike, Mass. Primary E.xaminer-Morris Liebman [22] F'led: 1970Assistant Examiner-Richard Zaitlen [21] AppL 13,179Attorney-Lane,Aitken,'Dun'ner&Ziems [57] ABSTRACT [52] US. Cl.....'..260/33.2, 252/2, 252/8,

260/295 A, 260/41 A A shelf stable slurry for injection into ablativewater fire extin- [51] int. Cl ..C08g 51/42 gu g sy ems comprises auniform suspension of [58] Field of Search ..260/33.2, 33.4, 41 A, 29.6S; p lyacrylamide polymer gelling agent in a polyoxyalkylenc 106/30vehicle containing a stabilizing amount of silica suspending agent. [56]References Cited UNITED STATES PATENTS 17 Claims Drawings 2,810,71610/1957 Markus ..260/88.1

SLURRY ADDITIVE FOR ABLATIVE WATER FIRE EXTINGUISHING SYSTEMS CROSSREFERENCE TO RELATED APPLICATION William L. Livingston et al.

Serial No. 766,475

Filed Oct. 10, 1968 Entitled: Method of Controlling Fire BACKGROUND OFTHE INVENTION In the aforementioned copending application, a method offire protection is disclosed in which a gelling agent in the fonn ofwater swellable polymer is injected into a water main supplying thesprinkler heads of a fixed fire extinguishing system actuated to put outa fire in the enclosure within which the sprinkler heads are located. Byso introducing the gelling agent into a flowing water stream in thewater main, an ablative gel fire extinguishant is formed havingsignificant advantages over plain water. Not only are the thermalabsorption characteristics of the ablative gel greater than water, butequally as important, the gel is substantially more viscous than plainwater and tends to cling to surfaces on which it is sprayed. As aresult, much lesser quantities of the ablative extinguishant arerequired to put out a fire than is required with plain water, therebyenabling system designs with lower flow capacity, not to mention asignificant reduction in water damage to the space protected.

Although systems embodying the method described in the aforementionedcopending application have been found extremely effective inextinguishing actual fires, numerous and complex practical problems havebeen encountered in the achievement of proper gelling agent injection atthe time the system is actuated to extinguish a fire. For example, thegelling agent itself is highly reactive to water and can create waterstoppages in the fire extinguishing system over-injection occurs.Moreover, the powdered solid form of the gelling agent and the innatedifiiculty of properly mixing a powder with a liquid stream underpressure is, at the very least, likely to provide large slugs ofrelatively rigid material, contributing further to the problem of pipeblockage. Obviously, even the most remote possibility of pipe blockagescannot be tolerated in fire extinguishing systems.

In the earlier stages of development, the problems of mixing the gellingagent with the flowing stream were solved in part by first mixing thepowder with a separate liquid carrier such as anhydrous propyl alcoholto form a slurry, and introducing the slurry into the flowing waterstream. Principally because of the very short shelf life of knownslurries, actual formation of the slurry in systems heretofore availabledid not occur until after the fire extinguishing system had been beenactivated. One obvious shortcoming of this approach is as a result ofthe number of mechanisms which must be brought into operation before thedesirable attributes of the ablative water system can be consummated. Inthis connection, moreover, it must be borne in mind that fixed fireextinguishing systems, by virtue of their being operated only duringperiods of dire emergency, remain inactive for long periods of time,often exceeding several years duration. Consequently, conventional itemsof hardware, capable of effecting first the mixture of the powderedsolid gelling agent to form a slurry and then the introduction of theslurry into the water lines supplying the sprinkler heads of the fireextinguishing system, present an extremely high percentage of risk interms of possible malfunction at the time they are called on toextinguish a tire. Hence, there is an acute need for a gelling agentcontaining slurry having a shelf life commensurate with the long dormantperiods of fixed fire extinguishing systems and also which possessessuch chemical and physical properties that the introduction thereof intoa flowing pipe line can be effected very simply and reliably upon theexistence of a fire without danger of pipe blockages.

SUMMARY OF THE INVENTION In accordance with the present invention, theproblems heretofore experienced with the injection of gelling agentsinto a flowing water stream to form an ablative extinguishant aresubstantially alleviated by the uniform suspension of polyacrylamidepolymer gelling agent in a polyoxyalkylene vehicle containing astabilizing amount of silica suspending agent to form a shelf stableslurry. The terms slurry" and suspension" are used hereininterchangeably.

DETAILED DESCRIPTION OF THE INVENTION The polyacrylamide polymer gellingagents for use herein are cross-linked, hydrolyzed compounds representedby the structural formula wherein n/m ranges from 2 to 4 with 2.5 to 3.5preferred. These compounds have molecular weights ranging from 15,000 to25,000 with 17,500 to 22,500 preferred. These gelling agents areconveniently utilized herein in particulate form having an averageparticle size ranging from through 50 mesh to through 325 mesh,preferably from through 230 mesh to through 325 mesh, U.S. StandardSeive Series. These gelling agents are readily commercially available.For example, a very suitable gelling agent within this class ofcompounds is sold under the trade name Gelgard M by Dow ChemicalCompany. Gelgard M has the above structural formula wherein n/m isapproximately 3. It has an average molecular weight of about 20,000 andis in particulate form having a particle size of through 325 mesh, U.S.Standard Seive Series.

The polyoxyalkylene vehicles in which the gelling agents are suspendedare polyoxyalkylene monohydroxy compounds which are aliphatic monoethersof polyoxyalkylene glycols. The aliphatic monoether groups contain oneto four carbon atoms. The polyoxyalkylene portion of the moleculecomprises a chain fonned predominantly of the oxyethylene group and theoxy-l, Z-propylene group. They are prepared utilizing a mixture ofethylene oxide and l,2-propylene oxide in which the weight ratio ofethylene oxide to l,2-propylene oxide ranges from 3:1 to 121.5,preferably 2:1 to 1:125. Useful compounds have viscosities ranging from50 to Saybolt seconds at 100 F. (The viscosity is a measure of molecularweight.) and are water-miscible. These compounds are described inRoberts et al, U.S. Pat. No. 2,425,755. These compounds are readilycommercially available. An especially useful compound within this classis sold under the tradename UCON 50 HB 100. This compound is believed tohave its aliphatic monoether group derived from butanol (that is,containing 4 carbon atoms) and to be prepared utilizing a mixture ofethylene oxide and 1,2-propylene oxide with a weight ratio of ethyleneoxide to l,2-propylene oxide of 1:1; it has a viscosity of 100 Sayboltseconds at 100 F. and is water-miscible.

The silica suspending agent useful herein is colloidal pyrogenic silica.It is conveniently prepared by high temperature that is vapor phasehydrolysis of silicon tetrachloride. Ordinarily it has a surface arearanging from 100 square meters per gram to 300 square meters per gram,preferably ranging from square meters per gram to 225 square meters pergram. Pyrogenic silica suitable for use herein is sold under the tradename Cab-o-sil by Cabot Corporation. An especially useful pyrogenicsilica is sold under the trade name Cab-o-sil M-5. It has a surface areaof 200 square meters per gram.

The gelling agent should be present in the slurry in an amountsufficient that the slurry may be efficiently stored and transported andefficiently injected to form ablative water for extinguishing purposes.In other words, if very little of the III gelling agent active ispresent percentagewise in the slurry, the storing and shipping costswill be increased and more pumping will be required to get the gellingagent where it is to operate compared to where a greater percentage ofgelling agent is present. On the other hand, the amount of gelling agentpresent in the slurry should be insufficient for precipitation of thegelling agent from the slurry to occur. Ordinarily, these goals areobtained if the slurry comprises by weight from to 49 percent gellingagent, preferably from to 45 percent gelling agent.

The polyoxyalkylene vehicle should be present in amount sufficient forthe gelling agent to remain in suspension but insufficient to dilute theslurry to the point where it is not economically handled. Ordinarilythese goals are obtained if the slurry comprises by weight from 89 to 47percent vehicle, preferably from 62.5 to 51.5 percent vehicle.

The' silica suspending agent should be present in an amount sufficientto stabilize the slurry, that is suspension, against separation ofcomponents resulting in settling of the gelling agent into a discretebody, but insufficient to thicken the slurry to the point where it ispumped with difficulty. Ordinarily these goals are obtained if theslurry comprises by weight from 1 to 4 percent suspending agent,preferably from 2.5 to 3.5 percent suspending agent.

The slurry of the present invention is conveniently prepared by firstslowly blending the suspending agent into the vehicle until a homogenousmixture is achieved and then mixing in the gelling agent to provide auniform slurry.

The resulting slurry is pourable and is easily pumped. When the slurryis mixed with water in an amount sufficient to provide 0.1 to 0.5percent gelling agent in the resulting mixture, an ablativeextinguishant is formed capable of putting out enclosed fires. Theslurry is indefinitely shelf stable against separation of componentsresulting in settling of the gelling agent into a discrete body andagainst harmful viscosity change at temperatures normally encounteredduring shipping and storage in fire extinguishing systems previous touse.

The following example further illustrates a slurry additive within thescope of the present invention and its preparation and use.

EXAMPLE A 100-pound batch of slurry was made up as follows: 57 pounds ofUCON 50 HB 100 was poured into a cement mixer. To the UCON 50 BB 100 inthe cement mixer was added over a 5minute period 3 pounds of Cab-o-silM-5. The cab-o-sil was blended in slowly so that no lumps were formed.After the Cab-o-sil was uniformly distributed through the UCON 50 HB100, lbs. of Gelgard M was slowly blended in over a 30- minute period.After the blending was achieved, the mixing was stopped and a uniformslurry was provided. The slurry thus formed contained by weight 57% UCON50 HB 100, 40% by weight Gelgard M, and 3% Cab-o-sil M-5.

The slurry thus formed was injected from a P-inch diameter copper tubinginto the center of a water stream flowing in a 3- inch diameter steelpipe by means of a Moyno positive displacement slurry pump to form anablative material which was directed on a 12-foot high pile of ignitedpallets by spray nozzles centrally positioned above the top of the pileof pallets. Slurry was injected into the water stream so that thedensity of ablative material directed onto the blazing pile of palletswas approximately 0.2 gallons/minute/foot square. The amount of slurryadded to the water was about 0.5 percent by weight, and since theGelgard M represented about 40 percent by weight of the slurry, theamount of gelling agent actually added to the water was about 0.2percent by weight. A square spray pattern was obtained by using a solidpattern square spray nozzle manufactured by the Spray Systems Co. underN0. 2H290SQ. The ablative maten'al extinguished the fire.

The slurry so formed remains useful in the above-described system eventhough retained in a slurry storage tank upstream of the injector forperiods as long as 1 year. Thus, even 1 year after the slurry has beenplaced into the extinguishment system the slurry is still uniform, stillhas a pumpable viscosity, and is easily injected into a water stream toform an ablative material whereby fires in enclosures can beextinguished.

These same results are achieved when the composition of the slurry is byweight 52.3% UCON 50 HB 100, 45% Gelgard M, and 2.7% Cab-o-sil M-5.

Other polyacrylamide polymer gelling agents than Gelgard M, otherpolyoxyalkylene vehicles other than UCON 50 HB 100, and other pyrogenicsilicas than Cab-o-sil M-5 can be utilized in the above example withsimilar results of shelf stability over long periods of storage in anextinguisher system prior to use resulting in pumpability and theformation of suitable ablative mixtures even after having remained inthis system more than 1 year.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiments are therefore to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription, and all changes which come within the meaning and range ofequivalency of the claims are therefore intended to be embraced therein.

What is claimed is:

1. A shelf stable slurry additive for ablative water automatic fixedfire extinguishing systems, said additive comprising a uniformsuspension of polyacrylamide polymer gelling agent in a polyoxyalkylenevehicle containing an amount of silica suspending agent sufficient tostabilize said suspension.

2. The slurry additive of claim 1 wherein the silica suspending agent iscolloidal pyrogenic silica.

3. The slurry additive of claim 2 wherein said pyrogenic silica has asurface area ranging from about square meters per gram to about 300square meters per gram.

4. The slurry additive of claim 3 wherein said additive comprises byweight from about 1 to 4 percent pyrogenic silica.

5. The slurry additive of claim 4, said additive comprising by weightfrom about 2.5 to 3.5 percent pyrogenic silica.

6. The slurry additive of claim 1, wherein the gelling agent is across-linked, hydrolized compound having the structural formula whereinn/m ranges from about 2 to 4, said compound having a molecular weightranging from about 15,000 to 25,000.

7. The slurry additive of claim 6 wherein said gelling agent is inparticulate form having an average particle size ranging from throughabout 50 mesh to through about 325 mesh.

8. The slurry additive of claim 7 wherein the gelling agent particlesize ranges from through about 230 mesh to through about 325 mesh.

9. The slurry additive of claim 6 wherein said additive comprises byweight from about 10 to 49 percent gelling agent.

10. The slurry additive of claim 9 wherein said additive comprises byweight from about 35 to 45 percent gelling agent.

11. The slurry additive of claim 1 wherein the polyoxyalkylene vehicleis a polyoxyalkylene monohydroxy compound which is an aliphaticmonoether of a polyoxyalkylene glycol, the aliphatic monoether groupcontaining 1 to 4 carbon atoms, the polyoxyalkylene portion of themolecule comprising a chain formed predominantly of the oxyethylenegroup and the oxyl ,2-propylene group.

12. The slurry additive of claim 11 wherein said vehicle is preparedutilizing a mixture of ethylene oxide and 1,2- propylene oxide in whichthe weight ratio of ethylene oxide to l,2-propylene oxide ranges fromabout 3:1 to 1:15, said vehicle having a viscosity ranging from about 50to Saybolt seconds at 100 F., said vehicle being water-miscible.

13. The slurry additive of claim 12 wherein the weight ratio of ethyleneoxide to 1,2-propylene oxide ranges from about 2:1 to 1:125 and whereinsaid vehicle has a viscosity ranging from about 75 to 125 Sayboltseconds at 100 F.

14. The slurry additive of claim 13 wherein said additive comprises byweight from about 47 to 89 percent vehicle.

15. The slurry additive of claim 14 wherein said additive comprises byweight from about 62.5 to 5 1.5 percent vehicle.

16. The slurry additive of claim 1 wherein the gelling agent is across-linked, hydrolzyed compound represented by the structural formulaparticulate form having a particle size of through about 325 mesh; saidpolyoxyalkylene vehicle being an aliphatic monoether of apolyoxylalkylene glycol, the monoether group being derived from butanol,the polyoxyalkylene portion of the molecule being derived from butanol,the polyoxyalkylene portion of the molecule being derived from a mixtureof ethylene oxide and 1,2-propylene oxide with a weight ratio ofethylene oxide to 1,2-propylene oxide of about 1:1, said polyoxyalkylenevehicle having a viscosity of about Saybolt seconds at 100 F. and beingwater-miscible; the silica suspending agent being colloidal pyrogenicsilica having a surface area of about 200 square meters per gram; saidslurry additive comprising by weight from about 35 to 45 percent gellingagent, from about 51.5 to 62.5 percent vehicle, and from about 2.5 to3.5 percent silica suspending agent.

17. A method for preparing the slurry additive of claim 1,

said method comprising the steps of first blending the W suspendingagent into the vehicle until a homogenous mixture is achieved and thenmixing in the gelling agent to provide a uniform slurry.

2. The slurry additive of claim 1 wherein the silica suspending agent iscolloidal pyrogenic silica.
 3. The slurry additive of claim 2 whereinsaid pyrogenic silica has a surface area ranging from about 100 squaremeters per gram to about 300 square meters per gram.
 4. The slurryadditive of claim 3 wherein said additive comprises by weight from about1 to 4 percent pyrogenic silica.
 5. The slurry additive of claim 4, saidadditive comprising by weight from about 2.5 to 3.5 percent pyrogenicsilica.
 6. The slurry additive of claim 1, wherein the gelling agent isa cross-linked, hydrolized compound having the structural formula
 7. Theslurry additive of claim 6 wherein said gelling agent is in particulateform having an average particle size ranging from through about 50 meshto through about 325 mesh.
 8. The slurry additive of claim 7 wherein thegelling agent particle size ranges from through about 230 mesh tothrough about 325 mesh.
 9. The slurry additive of claim 6 wherein saidadditive comprises by weight from about 10 to 49 percent gelling agent.10. The slurry additive of claim 9 wherein said additive comprises byweight from about 35 to 45 percent gelling agent.
 11. The slurryadditive of claim 1 wherein the polyoxyalkylene vehicle is apolyoxyalkylene monohydroxy compound which is an aliphatic monoether ofa polyoxyalkylene glycol, the aliphatic monoether group containing 1 to4 carbon atoms, the polyoxyalkylene portion of the molecule comprising achain formed predominantly of the oxyethylene group and theoxy-1,2-propylene group.
 12. The slurry additive of claim 11 whereinsaid vehicle is prepared utilizing a mixture of ethylene oxide and1,2-propylene oxide in which the weight ratio of ethylene oxide to1,2-propylene oxide ranges from about 3:1 to 1:1.5, said vehicle havinga viscosity ranging from about 50 to 150 Saybolt seconds at 100* F.,said vehicle being water-miscible.
 13. The slurry additive of claim 12wherein the weight ratio of ethylene oxide to 1,2-propylene oxide rangesfrom about 2:1 to 1: 1.25 and wherein said vehicle has a viscosityranging from about 75 to 125 Saybolt seconds at 100* F.
 14. The slurryadditive of claim 13 wherein said additive comprises by weight fromabout 47 to 89 percent vehicle.
 15. The slurry additive of claim 14wherein said additive comprises by weight from about 62.5 to 51.5percent vehicle.
 16. The slurry additive of claim 1 wherein the gellingagent is a cross-linked, hydrolzyed compound represented by thestructural formula
 17. A method for preparing the slurry additive ofclaim 1, said method comprising the steps of first blending thesuspending agent into the vehicle until a homogenous mixture is achievedand then mixing in the gelling agent to provide a uniform slurry.